1. Field of the Invention:
The present invention relates to thickener for cleaning compositions, the thickener having a shear-thinning, viscoelastic rheology with long relaxation times, and in particular to cleaning compositions thickened therewith incorporating a bleach and which are formulated to have utility as drain cleaners, or which are formulated to have utility as hard surface cleaners.
2. Description of Related Art:
Much art has addressed the problem of developing a thickened cleaning composition, which may contain a bleach and may have utility as a hard surface cleanser. The efficacy of such compositions is greatly improved by viscous formulations, increasing the residence time of the cleaner. Splashing during application and use is minimized, and consumer preference for a thick product is well documented. U.S. Pat. No. 4,375,421, issued to Rubin et al describes a viscous, nonhypochlorite-containing composition containing at least five percent of amido and sulfobetaines, and water-soluble organic or inorganic salts such as sulfates and carbonates. Alkaryl sulfonates are specifically mentioned as possible surfactants for the composition. Rubin et al is distinguishable, however, in that there is no disclosure of the composition being viscoelastic, and alkyl betaines are specifically excepted from those which are useful. Schilp, U.S. Pat. No. 4,337,163 shows a hypochlorite thickened with an amine oxide or a quaternary ammonium compound, and a saturated fatty acid soap, and mentions that a C.sub.8-18 alkyl betaine may be incorporated at levels about equal to the amine oxide (1.5 wt. %). Stoddart, U.S. Pat. No. 4,576,728 shows a thickened hypochlorite including 3- or 4-chlorobenzoic acid, 4-bromobenzoic acid, 4-toluic acid and 3-nitrobenzoic acid in combination with an amine oxide, and mentions that a C.sub.8-18 alkyl betaine may be incorporated at levels about equal to the amine oxide (1.5 wt. %) Neither Schilp nor Stoddart disclose any thickening or rheological benefits by the optional inclusion of their betaines. DeSimone, U.S. Pat. No. 4,113,645 discloses a method for dispersing a perfume in hypochlorite using a quaternary ammonium compound. Bentham et al, U.S. Pat. No. 4,399,050, discloses hypochlorite thickened with certain carboxylated surfactants, amine oxides and quaternary ammonium compounds. Jeffrey et al, GB 1,466,560 shows bleach with a thickener comprising a sarcosinate or tauride surfactant, and a soap, quaternary ammonium compound, betaine, amine oxide, or alkanolamide. Farkas, U.S. Pat. No. 2,834,737 describes an unthickened hypochlorite bleach having about 0.05-1% of a C.sub.10-16 alkyl betaine as a foaming agent and to mask the hypochlorite odor. Hynam, U.S. Pat. No. 3,684,722 describes an alkali-metal hypochlorite which is thickened by a surface active agent, which may be a C.sub.8-18 alkyl betaine and a C.sub.8-18 soap. Hardy et al, EP 129,980 discloses hypochlorite, an amine oxide or betaine, and an organosilicon quaternary ammonium compound as a bacteriocide, and is limited to an ionic strength of below about 5.0 g moles/dm.sup.3. Gray, GB No. 1,548,379 describes a thickened bleach incorporating a sucrose surfactant with a quaternary ammonium compound, an amine oxide, a betaine, an alkanolimide, or combinations thereof.
For various reasons, the prior art thickened hypochlorite compositions are not commercially viable. In many instances, thickening is insufficient to provide the desired residence time on non-horizontal surfaces. Adding components, and/or modifying characteristics of dissolved components often creates additional problems with the composition, such as syneresis, which require adding further components in an attempt to correct these problems. Polymer thickened hypochlorite bleaching compositions tend to be oxidized by the hypochlorite. Prior art thickened bleach products generally exhibit phase instability at elevated (above about 49.degree. C.) and/or low (below about 2.degree. C.) storage temperatures. Difficulties exist with colloidal thickening agents in that these tend to exhibit either false-bodied or thixotropic rheologies, which, at high viscosities, can result in a tendency to set up or harden. Other hypochlorite compositions of the prior art are thickened with surfactants and may exhibit hypochlorite stability problems. Surfactant thickening systems also are not cost effective when used at the levels necessary to obtain desired product viscosity values. European patent application No. 204,472 to Stoddart describes shear-thinning compositions, and seeks to avoid viscoelasticity in such shear-thinning compositions.
Drain cleaners of the art have been formulated with a variety of actives in an effort to remove the variety of materials which can cause clogging or restriction of drains. Such actives may include acids, bases, enzymes, solvents, reducing agents, oxidants and thioorganic compounds. Such compositions are exemplified by U.S. Pat. Nos. 4,080,305 issued to Holdt et al; 4,395,344 to Maddox; 4,587,032 to Rogers; 4,540,506 issued to Jacobson et al; 4,610,800 to Durham et al; and European patent applications 0,178,931 and 0,185,528, both to Swann et al. Generally, workers in this field have directed their efforts toward actives, or combinations of actives, which would have improved efficacy or speed when used on typically-encountered clog materials; or are safer to use. A problem with this approach, however, is that regardless of the effectiveness of the active, if the composition is not fully delivered to the clog, the effectiveness of the active will be diminished. This is particularly apparent where the clogged drain results in a pool of standing water, and a drain opener composition added to such standing water will be substantially diluted thereby. The above European Patent Applications of Swann et al disclose an attempt to overcome the delivery problem by encapsulating actives in polymeric beads. The Rogers and Durham et al patents refer to the delivery problem and mention that a thickener is employed to increase the solution viscosity and mitigate dilution. Similarly, a thickener is optionally included in the formulation of Jacobson et al.